Increasingly Salty Mediterranean Favors Ice Sheet Growth

ScienceDaily (Oct. 28, 2002) — MINNEAPOLIS

ST. PAUL — About 150,000 years ago, an anomalous ice age was triggered by an increasingly salty Mediterranean Sea, a development that’s occurring today and may start new ice sheet growth in the next few decades, according to a study at the University of Minnesota. Robert Johnson, an adjunct professor of geology and geophysics, will present his study of the glaciation 150,000 years ago and discuss its implications for today’s climate on Tuesday, Oct. 29, at the annual meeting of the Geological Society of America in Denver.

Today, the formation of sea ice and pack ice in the Arctic Ocean depends on the presence of less salty–and therefore less dense–water near the surface. This density gradient arises from inputs of fresh water from rivers flowing into the Arctic Ocean from Canada and Siberia. The salty flow of the Mediterranean and Gulf Stream mixture tends to inhibit the formation of sea ice and pack ice. The rising salinity of the Mediterranean outflow, as measured by European oceanographers over the last 40 years, tends to increase the Arctic Ocean salinity, reduce the density gradient, and melt the pack ice there.